Research On The Generation Of Complex Grid Systems For Reservoir Simulation

Grid generation is the base of simulation and the quality of gird has direct influence upon the precision of simulation. At present, numerical simulation based on unstructed grid system is an important tendency of reservoir simulation and an indispensable functional module of simulation software. Corner Point Geometry, PEBI Grid, CVFE Grid are so flexible that they can exactly describe reservoirs with complex configuration (boundary, fault, fracture). It is important to research the method of creating high quality triangular grid because these three kinds of gird can be created on the basis of triangular gird. This paper presents a creating method meeting Delaunay condition-Controlled Subdomain Delaunay Triangulation Method. This method can save grid number, speed computation and create better grid in contrast with other methods. PEBI grid system is formed by connecting circumcenters of adjacent triangles and link the barycenter with midpoints of each edge to shape CVFE grid system, furthermore, the edges should be specially disposed. Three-dimensional Corner Point Geometry grid system is the most mature unstructed grid system and it can be created directly from quadrilateral grid system. PEBI and CVFE grid system are utilized in this paper to the reservoirs with complex shaped boundary, fractures and faults. The results demonstrate that it is more accurate than Cartesian grid and corner point geometry. The method of generating corner point geometry system is studied in this paper which is also evaluated through comparison with corner point geometry modular of the existing commercial simulation software. Furthermore, grid generation software covering Delaunay triangulation, PEBI grid, CVFE grid and corner point geometry is programmed especially for complex reservoirs with irregular boundaries. Three simulation examples are erected with this simulator: example 1 shows that PEBI gird system effectively reduces grid orientation effects; example 2 demonstrates PEBI grid can exactly simulate the effect of fault and high permeable strip to flow in complex reservoir; example 3 successfully used PEBI grid in five-spot pattern which verified the validity and reliability of this simulator.